Alaska's Cleveland Volcano raises alarms

The isolated volcano has formed a new lava dome, scientists report, possibly foreshadowing an eruption and ash cloud that could disrupt air travel.

HOT IN CLEVELAND: Alaska's Cleveland Volcano, seen here shrouded in clouds, may be on the verge of erupting, scientists say. (Photo: Mandy Lindeberg, NOAA/NMFS/AKFSC)

Authorities have raised the alert level for Cleveland Volcano in Alaska's Aleutian Islands, suggesting it may be on the verge of erupting ash and disrupting air travel. Also known as Mount Cleveland, the 5,676-foot volcano has recently developed a new lava dome, just a few weeks after its previous dome exploded in December.

Cleveland's alert level is now orange, which indicates a "watch" rather than a yellow "advisory." It's one of the most active volcanoes in the Aleutians, and it has been especially mercurial in recent months, frequently prompting scientists to switch its alert status.

"Renewed eruptive activity of Cleveland Volcano has been observed in satellite data," the U.S. Geological Survey warns, citing the growth of a lava dome that has now reached 130 feet (40 meters) in diameter. "It remains possible for intermittent, sudden explosions of blocks and ash to occur at any time, and ash clouds exceeding 20,000 feet above sea level may develop."

While its remote location means it poses little direct danger to people, a large ash cloud could spell trouble for intercontinental flights through Alaska. As CNN reports, about 90 percent of air freight from Asia to North America and Europe passes through Alaska airspace, while hundreds of flights carry more than 20,000 passengers through Anchorage daily. "If there is an explosion and [ash] reaches high altitudes, it will causes flights to be rerouted and ultimately canceled," Steve McNutt of the University of Alaska-Fairbanks tells CNN.

Cleveland Volcano's last significant eruption occurred in February 2001, according to the USGS, when it produced three "explosive events" that spewed ash clouds up to 39,000 feet, or roughly seven miles, into the sky. It also generated a "rubbly lava flow and hot avalanche that reached the sea." Another outburst in 2006 was captured on film by astronauts aboard the International Space Station:

Photo: J.N. Williams, ISS-13/NASA

Cleveland has also been rumbling back to life in recent months, however. After it spent much of 2011 building up a new lava dome, the volcano began slowly erupting in late July, followed by larger explosions in December that destroyed much of the existing dome in its crater. And now that a new dome has already formed again, scientists are concerned it could plug the volcano's conduit, causing pressure to accumulate and setting up an explosive eruption like the one in 2001.

Air travelers have become all too familiar lately with the effects of ash clouds. Iceland's Grimsvotn volcano forced hundreds of flight cancellations last year, about 13 months after another Iceland volcano, Eyjafjallajokull, wreaked havoc with air traffic worldwide when its ash clouds kept thousands of jets grounded across Europe.

The USGS reports that, so far, "there have been no observations of ash emissions or explosive activity during this current lava eruption." But it's also worth noting that Cleveland has no real-time seismic monitoring network, so scientists must rely on satellite data to tell them what's going on. And, the USGS adds, "explosions and their associated ash clouds may go undetected in satellite imagery for hours."

The Alaska Volcano Observatory does have a webcam trained on Mount Cleveland, but as Erik Klemetti of Wired points out, "in the Aleutians, getting a clear view can be very difficult." The webcam's website also says it's currently experiencing technical difficulties; as of Wednesday morning, the feed looked like this: